JPS60237439A - Resist material and formation of fine pattern using it - Google Patents

Abstract

PURPOSE:To enhance plasma resistance of a positive type resist by adding trimethylsilylnitrile to a soln. composed of a photosensitive resin as the material of the resist pattern, an org. solvent, etc. in a specified weight ratio. CONSTITUTION:The photosensitive resin is prepared by mixing a phenol resin, such as a phenol formaldehyde resin, having phenolic hydroxyl groups with a photosensitive agent, such as a naphthoquinonediazide-sulfonic acid deriv. represented by the formula (R is a group having a hydroxyl group) in a weight ratio of 1:(2.5-3). An intended resist material is obtained by dissolving this photosensitive resin in an org. solvent, such as cellosolve acetate, and adding trimethylsilylnitrile into this soln. in an amt. of 5-50wt% of the total solid of this soln. and itself. The use of this resist material permits application of it to a 2-layer structure resist process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a resist material used for forming a fine pattern on an integrated circuit and a method for forming a fine pattern using the resist material.

(Technical Background) Conventionally, in patterning and forming integrated circuits, a resist process has generally consisted of a single-layer resist film. However, in recent years, as semiconductor integrated circuits have become more highly integrated, semiconductor technologies such as metal multilayer films have been required. In this case, steps are likely to occur on the surface of the semiconductor integrated circuit, and these steps are becoming extremely large, reaching as much as 0.5 to 4.rho., for example. Gradual steps may cause various problems when patterning a substrate using a single resist film. For example, when a resist solution is applied onto a wafer with the above-mentioned steps, uneven portions occur in the thickness of the film, and exposure energy is easily reflected from the semiconductor substrate surface, resulting in fluctuations in the pattern width of the process-finished layer. was there.

In order to improve this drawback, a so-called three-layer resist pattern Jung method has been proposed and will be explained using an example shown in FIG.

First, a resist film 2 is formed by applying a first resist material mainly made of organic material to a thickness of 2 to 4 μm on the semiconductor substrate 1 . Next, an inorganic film 3 such as 5102 or a metal film 3 such as aluminum is formed to a thickness of several hundreds to 0.2 m. Further, a resist film 4 made of a photosensitive resist material is formed to a thickness of 0.2 to 1
Form on the outskirts.

In the resist process using such a three-layer structure, first, the third resist film 4 is patterned by exposing and developing a so-called pattern using a method similar to the conventional method. Next, the patterned third resist film 4 (Fig. 1e
) is used as a mask to pattern the second inorganic film 3. Specifically, this pattern forming method is based on wet etching or dry etching (using plasma).

Finally, using these second films 3 as masks, the first cyst films 2 are etched using oxygen plasma or active ion etching (RIE) as shown in FIG.
patterning is performed. The first drawing shows the etched state of the substrate. In the case of B, the membrane 31 is made of 5102, A), etc. as described above, and is treated with the oxygen plasma described above in 1. tl
It is hardly etched, ie it is plasma resistant (highly resistant to 02 RIE) and serves as a suitable mask layer. Note that the third film 4 cannot be used as an RIE mask because it is etched by oxygen plasma.

This 3N resist patterning method is based on the first method described above.
The resist film 2 is used to form a film that flattens the steps on the semiconductor surface, and the second and third resist layers are formed.
The patterning of the resist layer is performed with extremely high precision.

Then, the second and first layers 3,
2, a highly accurate pattern can be obtained. However, such a three-layer patterning method has disadvantages in that the process is complicated and the throughput is low.

(Object of the Invention) The present invention was made to solve the above-mentioned problems, and specifically provides a resist material with oxygen plasma resistance that enables a two-layer resist process, and a pattern forming method using the resist. It is in.

(Summary of the Invention) The gist of the invention of Party B is that the portion corresponding to the third resist layer has a 0. ．． It is characterized by having RIE characteristics, and thereby enables a two-layer resist patterning method instead of the three-layer patterning described above.

As described in detail later, such a resist material includes a photosensitive agent def-1-quinonediazide sulfonic acid represented by the formula, in a ratio of 1:2.5 to 3 by weight to a base resin such as phenol formaldehyde resin. A suitable solution is to add 5 to 50% by weight of trimethylsilylnitrile and dissolve the mixture in a solvent.

As the above-mentioned solvent, cellosolve acetate, MEK, xylene, n-butyl acetate, etc. are used alone or in combination.

AZ13 is generally well known as a UV resist.
5. The material represented by OJ (trade name of Hoechst Co., Ltd.) is a system in which phenol formaldehyde is used as a resin base material and a photosensitive material naphthoquinonediazide sulfonic acid derivative is mixed therein. The resist ζ has superior resolution, and its usage has been increasing in recent years. However, the oxygen etching rate of this type of resist is 2000 to 3000 people/mi.
It has a high value of n and does not have the properties as the above-mentioned 02 RIE mask.

This characteristic can be achieved by mixing the cyst of the present invention with a silicon compound and trimethylsilylnitrile as described above.

The present invention will be specifically explained below using examples.

(Example) Example 1 A phenol formaldehyde resin of the following formula as a base material, (in the formula 2≦n<13) a photoactive compound,
JJ, below PAC), naphthoquinonediazide sulfonic acid derivatives of the following formula were mixed and adjusted at a ratio of 1:2.5 to 3% by weight (the same applies hereinafter), and 5% of trimethylsilylnitrile was added.
A resist solution was prepared by dissolving the ~50% mixture in Cellsolve acetate, methyl ethyl ketone, xyleno, or N-butyl acetate alone or in a mixed solvent thereof as a solvent. The obtained resist solution was spin-coated onto the sea urchin, baked at 50°C for 30 minutes, exposed to ultraviolet light, and further developed by dipping in a developer (alkaline diluted solution) for 1 minute to obtain a predetermined pattern. .

The pattern obtained was positive, and its resolution was equivalent to or better than that of conventional resists. Then 02 RI
The Etchley-1. was measured by E.

FIG. 2 shows the etch rate relative to trimethylsilinitrile (wt%). According to the results in the same figure, when the trimethylsilyl nitrile is around 30 to 35 W%, the etch rate is about 50 people/min, which is sufficient oxygen resistance RI.
It showed E characteristics.

Since the etch rate of a normal resist is 7 min for 2000 to 3000 people, the etch rate is reduced to 1/40 to 1/60 of that.

Next, patterning using a two-layer resist was investigated using the above-described resist of the present invention. In FIG. 3, a first conventional regimen 1-12 is deposited on a wafer 11 to a thickness of 2) a to 5.
It was applied to the skin and baked for 30 minutes at a baking temperature of 150°C. Next, the above-described resist 13 according to the present invention was similarly spin-coated onto the first resist B to a thickness of 0.5 to 1 ρ to form a second resist solution, and exposed to ultraviolet light in a desired pattern. The second resist film 13 was immersed in a developer for about 1 minute in a conventional manner to perform pakurening. Next, using the pattern 13 of the second resist film as a mask,
The resist film 12 was etched by 02 RIE.

Furthermore, using the first and second resist film patterns as masks, the semiconductor substrate was etched as shown in FIG. 3f.

The patterning formed as described above is
Because this resist film has sufficient resistance to oxygen plasma, it is possible to use the above-mentioned first resist as a mask for etching by oxygen RIE.
There was an advantage that the O2 film was not required and those complicated processes were simplified.

Example 2 The same procedure as in Example 1 was carried out except that phenol form of the following formula was used as the photosensitive resin. The results showed characteristics equivalent to those of Example 1, and similar results were obtained.

Example 3 Commercially available UV positive resist, e.g. AZ 1350J,
AZl, 470, (Hoechst), MP1400
(Sillaplay), KPR820 (Kodak), H
PR2,06 (Hunt) or 0FPR800,0
Each sample was carried out in the same manner as in Example 1 except that NPR830 was used as the photosensitive regimen, and the results showed the same characteristics and obtained the same results as in Example 1.

Furthermore, as the above-mentioned exposure energy, in addition to ultraviolet rays, electron beam,
Although it was carried out using an ion beam, it was possible to form a pattern similar to that in the first embodiment.

(Effects of the Invention) As described above, the resist of the present invention exhibits excellent properties such as sufficient resistance to oxygen plasma, and the use of this resist has the advantage of enabling a two-layer resist patterning method. Yes, the complexity of the process in the above-mentioned three-layer resist patterning can be significantly simplified,
For example, when used in the production of VLSIs, it has good workability and produces remarkable effects such as cost reduction and reduction in defect rate.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the conventional three-layer resist patterning method, FIG. 2 is a characteristic diagram of the resist of the present invention, and FIG. 3 is a schematic diagram of the two-layer patterning method of the present invention. 1.11 Wafer, 2, 3, 4, 12°13 ・Resist film Fig. 1 Fig. 2 0. 10 20 30 40 50 TRIMETHYL 5ILYL NITRILE (
W'/J Figure 3 procedural amendment (voluntary) June 14, 1985 Commissioner of the Japan Patent Office Shiga Means 1 Indication of case Patent Application No. 1982-82836 2 Title of invention Resist material and method for forming fine patterns using the resist 3 Relationship with the case of the person making the amendment Patent applicant (029) Oki Electric Industry Co., Ltd. 4 Full text of the attorney's specification, drawings (plan) Description 1, Name of the invention Resist material and method for forming fine patterns using the resist 2. Claims (1) A resist solution that is a material for a positive resist pattern has a total weight ratio of 5 to 50% including the solid components of this solution.
A resist material characterized by adding trimethylsilylnitrile. (2) The resist material according to claim 1, wherein the resist solution comprises a photosensitive resin and an organic solvent. 121 The resist material according to claim 1, item 2, wherein the photosensitive resin q comprises a phenolic resin having a phenolic hydroxyl group and a photosensitizer. (4) The ratio of the photosensitive resin and the photosensitive agent is 1:2.5
'3. 4. The resist material according to claim 3, wherein the phenolic resin 1 is a phenol formaldehyde resin as shown below. (6) The resist material according to claim 3, wherein the photosensitizer is a nara-1-quinonediazide sulfonic acid derivative represented by: (7) The resist material according to claim 2, wherein the photosensitive resin is a phenol formaldehyde ester represented by the following. (81fm The organic medium is Celsono L acetate,
3. The resist material according to claim 2, which is a mixed solvent of one or more of methyl ethyl ketone, xylene, and n-butyl acetate-1. (9) A step of applying the 11975th layer on the substrate and flattening the substrate; a step of forming a second resist layer by applying a resist material containing 5 to 50% trimethylsilylnitrile in total; a step of patterning this second resist layer to obtain a second resist pattern; No. 1197 using resist pattern No. 2 as a mask
A method for forming a fine pattern, comprising the steps of patterning five layers, and then performing plasma etching on the substrate using a second resist pattern as a mask. (10) The thickness of the 21st nodist layer is 0.5 to 1.0
The method for forming a fine pattern according to claim 9, wherein the method is //ITI. 3. Detailed Description of the Invention (Field of Industrial Application) The invention of B relates to a resist material having high plasma resistance and a method for forming a 1vI fine pattern using the resist material. (Prior Art) Conventionally, as a method for patterning a conductor substrate, there is a patterning method using a three-layer resist structure. FIG. 2 is a cross-sectional view of the process of patterning this three-layer resist structure. Hereinafter, the conventional technology will be explained with reference to this drawing. First, in order to flatten the semiconductor substrate 1 with a first resist material mainly made of organic material, 2 to 4/J
n to form the Runst layer 2 (FIG. 2(a)). Next, the intermediate layer 3, which is an inorganic film such as Si or a metal film such as Ae, is coated to a thickness of several hundred to 0.2 Form to the level of captivation (Second
Figure (father-in-law). Furthermore, a 1ζ photosensitive resist material is applied to a thickness of 0.
．． 2 to 1.0//ln to form the second resist layer 4 (FIG. 2(C)). The second resist layer 4 is exposed and developed to form a pattern (FIG. 2(dl)), and the intermediate layer 3 is patterned using this pattern as a mask (FIG. 2(e)). And finally the 21st patterned
/ Active ion etching (RoT,
Patterning of the second resist R2 is performed by E, ) (Fig. 2 (season). However, since the second resist layer 4 has low plasma resistance, it cannot serve as a mask for R,1,E. Because the intermediate layer 3 has high plasma resistance, it remains almost unetched by the oxygen plasma R, R, and E, and does not play a role as a mask. The following are the advantages of the above-mentioned patterning method for the three-layer metal structure. Film technology is required, and the semiconductor integrated circuit surface (substrate surface)
A level difference reaching up to p occurs. These steps not only cause unevenness in film thickness when applying a resist film, but also reflect exposure energy during exposure, causing variations in the width of the pattern. In the patterning method for a three-layer resist structure, in order to remove such steps, a first resist layer is formed, the substrate surface is flattened, and then the upper intermediate layer and second resist layer are patterned, resulting in highly accurate patterning. can be done. (Problems to be Solved by the Invention) However, the above-mentioned method has disadvantages in that three layers are laminated and the layers are sequentially etched, so the process is complicated and the throughput is low. (Means for solving the problem) In order to solve the problem, the inventors have conducted repeated research and found that the total weight ratio of the conventional resist)-solution and its solid components is 5 to 5.
It has been found that using a resist material containing 50% trimethylsilylnitrile as an additive is effective in forming fine patterns. Specifically, in the fine pattern forming method, the above-mentioned resist is applied onto the flattened substrate on which the second resist layer has been formed to form a second resist layer, and after patterning this second resist layer, the second resist layer is formed. The method is characterized in that the first resist layer is patterned using the pattern as a mask, and finally the substrate is plasma etched using the pattern of the second resist layer as a mask. (Function) Plasma resistance is significantly improved by adding the additive trimethylsilylnitrile to a conventional resist solution. Here, although it is not necessarily clear how trimethylsilyl nitrile acts, it is thought that Si in trimethylsilyl nitrile improves plasma resistance. (Example) The resist material according to the present invention can be obtained by adding trimethylsilylnitrile in a total weight ratio of 5 to 50% with the solid components of the solution (B) to a positive resist solution (hereinafter referred to as base material solution). The base material solution used is a photosensitive resin dissolved in an organic solvent. Here, the photosensitive resin is phenol formaldehyde ester. Examples include a mixture of a phenolic resin having a phenolic hydroxyl group and a naphthoquinonediazide sulfonic acid derivative as a photosensitizer in a weight ratio of 1:2.5 to 3.0. In addition, organic solvents include cellosolve acetate, methyl ethyl ketone, and xylene. n-Butyl acetate can be used alone or in combination. Furthermore, a commercially available positive resist can be used as the base material solution. Specifically, “AZI350J”, “
AZ1470” (manufactured by Hoechst) “MP 1400”
(manufactured by Silaplay), "KPR820'" (manufactured by Kodak), "HPR206" (manufactured by Hunt Chemical)
Examples include CFR800".0NPR830" (manufactured by Tokyo Ohkasha). Conventional positive resists have an etching rate of 2,000 to 3,000 people/min for plasma etching. However, the resist of the present invention can be used at 500 people/min, fi
This serves as a mask for plasma etching. Example 1 A phenol formaldehyde resin of the following formula was used in a weight ratio of 1:
They were mixed at a ratio of 2.5 to 1:3. In this example, three types of phenol formaldehyde having polymerization numbers n of 4, 5, and 16 were used. This mixture was dissolved in Cellsolve acetate to prepare a resist solution, and trimethylsilylnitrile was added thereto. The amount of trimethylsilylnitrile is expressed as a weight ratio based on the total amount of trimethylsilylnitrile. The resist material prepared in this manner was applied in a range of 0.5 to 1.
Spin coated onto a wafer at a thickness of 0-30°C at 50°C.
Bake for a minute. Thereafter, the wafer was exposed to ultraviolet light and dip-developed in a developer (alkaline diluted solution) for 1 minute. The pattern thus obtained has a width of 0.7p,
The resolution was superior to that of conventional resists. FIG. 3 is a diagram showing the etch rate versus weight ratio of trimethylsilylnitrile in this example. As can be seen from this figure, the weight ratio of trimethylsilylnitrile is 5.
The etch rate was 500 people/min in the range of ~50%, showing good results. Especially when n=15,
When the weight of trimethylsilylnitrile was around 5 to 50%, the etch rate was about 50 people/min, and the film had sufficient plasma resistance. Example 2 A phenol formaldehyde ester of the following formula was used as a photosensitive resin. In this example, the polymerization number n of the phenol formaldehyde ester is 3.50.000.
Three types of 100,000 were used. This phenol formaldehyde ester was dissolved in xylene to prepare a resist solution, and trimethylsilylnitrile was added. As in Example 1, the amount of trimethylsilylnitrile is expressed as a weight ratio of the total amount to phenol formaldehyde. A pattern was obtained in the same manner as in Example 1 using the resist material of Example 2. The obtained pattern is 0 as in Example 1.
．． The width was 7.11111, and the resolution was still excellent. FIG. 4 is a diagram showing the etch rate with respect to the weight ratio of trimethylsilylnitrile in Example 2. When the weight ratio of trimethylsilylnitrile is in the range of 2 to 50%, the etch rate is 500 people/min as in Experimental Example 1, which indicates that the resist material of this example has good plasma resistance. Recognize. Especially n=50. In the case of ooO, the etch rate was about 70 people/min at around 27 to 40%, and it had very good plasma resistance. Example 3 Example 3 is an example using a commercially available resist material. Commercially available resist materials, such as AZ 1350 J. AZ1470 (Hoechst), MP1400 (Sillaplay), KPR820 (Kodak). HPR206 (Hunt), 0FPR800, 0NPR
A resist material was prepared by adding 1-limethylsilylnitrile to 830 (Tokyo Ohka@) (7). When this resist material was subjected to the same test as in Example 1, similar good results were obtained. A method of forming a fine pattern using the resist material of the invention of Part B as described above will be explained with reference to FIG.
2 (Fig. 1(a)). This second resist is applied for the purpose of flattening the substrate 11 as in the conventional case, and after being applied, it is baked at 150° C. for 30 minutes. Next, on this second resist 1, a resist material of the present invention is spin-coated as a second resist layer 13 to a thickness of 0.5 to 1.0 Ian (FIG. 1(b)). Thereafter, the second resist layer 13 was baked at 50° C. for 30 minutes, exposed to ultraviolet light in a desired pattern, and immersed in a developer (alkaline diluted solution) for about 1 minute. As a result, a second resist pattern 13A is obtained (FIG. 1(C)).
. Next, using the second resist pattern 13A as a mask, the resist layer 12 is coated with R using oxygen plasma.1. E. It was etched by Nyo (Fig. 1(d)). Further, the substrate 11 is subjected to R using F2 plasma, 1. Figure 1 shows the state etched with E. , the steps of coating and patterning for one layer can be omitted, resulting in extremely good workability and the formation of highly accurate patterns at low cost. 4. Brief description of the drawings Figure 1 shows one example of the method of the present invention. FIG. 2 is a cross-sectional view for explaining the steps of the conventional pattern forming method. FIG. 3 is the etch rate relative to the weight ratio of trimethylsilyl nitrile in one example of the present invention. FIG. 4 is a diagram showing the etch rate with respect to the weight ratio of trimethylsilyl nitrile in another example of the present invention. 1.11... Substrate, 2, 12... 1st layer, 3・
- Middle layer, 4, 13... second resist layer. Honkari Hizuki's Tarmuta no v7-Nkaanhe Taita's Kuri 1θth m
Cross-sectional view Figure 1 A Liao Lai's three-layer tosyst structure〃)・Turning J Ahead construction cross-sectional view Figure 2 0 10 20 30 40 50 Trinotylsilylnitrile (volume %) A column 1
Works, child ratequito 11m Figure 3

Claims (4)

[Claims] (1) A resist material characterized in that it is made by mixing an alkali-soluble phenolic resin, a diazide compound ester, and a trimethylsilyl diazide compound in an organic solvent. (2) 1% by weight based on alkali-soluble phenolic resin
2. A resist material comprising a quinonediazide compound ester/1 represented by the formula: and 5 to 50% by weight of trimethylsilylnitrile mixed in an organic solvent at a ratio of 1:2, 5 to 3. (3) Cellosolve acetate-1- as the solvent. 1. The resist material according to item (1), which uses MFK S-N-GOL acetate alone or in combination. (4) As the base resin, phenol formaldehyde represented by the formula (1
)・Materials listed in section ). (sl & A step of forming a first resist film on the board and baking it, a step of further forming a second resist film and baking it, and applying energy to this second resist film through a mask. a step of forming a pattern on the mask by irradiating a beam and developing; a step of leaving the semiconductor substrate in oxygen plasma and forming a pattern on a second resist using the first resist bag as a mask; etching the semiconductor substrate using the first and second patterns as masks, and etching the semiconductor substrate using the first and second patterns as masks, and etching the semiconductor substrate in a proportion of 1:2.5 to 3 by weight based on the base resin such as phenol formaldehyde resin. Add a photosensitizer, naphthoquinone cyacytosulfonic acid, and add 5 to 50% by weight of trimethylsilyl nitrile in proportions.
A fine pattern forming method characterized by using a resist material mixed with an organic solvent.